This invention relates to a hollow, blow-molded, bottle-shaped container of a biaxially oriented polyethylene terephthalate resin and a piece or parison to be blow-molded into the same bottle-shaped container.
Since a blow-molded, bottle-shaped container of biaxially oriented polyethylene terephthalate resin, (hereinafter referred to as "a PET"), has a number of excellent physical properties and characteristics, it has a wide range of applications.
Some of the excellent physical properties of a bottle-shaped container of a PET can be realized once the bottle-shaped container has been biaxially oriented and blow-molded. The bottle-shaped container of the PET has heretofore been produced for its physical properties by the steps of injection-molding a piece or parison, as a primary or prefabricated molded piece, and then biaxially orienting the primary piece or parison, by the so-called injection blow-molded method. The neck portion of the bottle-shaped container used as a mounting portion for a blowing mold, has not entirely been oriented but has been molded from the primary piece or parison to the hollow, blow-molded, bottle-shaped container. In this manner, the shoulder portion, continues with the neck portion of the bottle-shaped container, has not been sufficiently oriented by the injection blow-molded method. Accordingly, the neck portion and the shoulder portion of the bottle-shaped container cannot exhibit the excellent physical properties of the PET prepared by the biaxially blow-molding method.
The drawbacks and disadvantages of the bottle-shaped container, thus blow-molded at the neck and shoulder portions which have not been subjected to or sufficiently subjected to an orientation are, for example, a crazing which occurs due to the impregnation of alcohol in high density to the bottle-shaped container, a feasibility of various deformations and strains including elongation due to a lack of sufficient hardness of the bottle-shaped container, and a low thermal resistance due to the occurrence of thermal deformation taking place when a content liquid is filled at high temperature in the bottle for the purpose of sterilization. More concretly the neck portion and the shoulder portion of the conventional bottle-shaped container, thus blow-molded, has such drawbacks and disadvantages that, when high internal pressure is applied to the bottle-shaped container, as when a carbonated drink mixed with fruit juice is entered into the container by a hot charging process, the shoulder portion, molded without being subjected to sufficient orientation, becomes axially elongated and deformed by the internal pressure.